Device for automatically controlling electrical conditions of an electron beam unit

ABSTRACT

A device for automatically controlling electrical conditions of an electron beam unit having an electron gun wherein a main cathode is heated by a current of electrons emitted by an auxiliary cathode, the main cathode of the electron gun is supplied from a main cathode heating unit, the auxiliary cathode is supplied from an auxiliary cathode heating unit and a heating correction unit of said main cathode is connected to at least one of said units.

United States Patent hruknvsky et al,

Inventors:

Assignee:

Filed:

App]. No.1

lgor Pawllllvich Brukovsky; Pavel Borisovicln Yaknvlev; Kirill Davidovlcll Gutterman; Alexandr Vasllievich Perov, all of Moscow; Vladimir Fedorovich Zhukov, Rzhev Kalininskoi oblasti; Larisa Petrovna Nekrasova, Rzhev Kalininskoi ohlasti; Jull'y Dmitrievich lvalnovsky, Rzhev Kalininskoi oblasti, all of USSR.

Mosknvsky Energeticheslsy llnstitut, Moscow, 1.1.8.811.

July 16, 1971 Related US. Application Data Continuation of Ser. No. 841,816, July 15,

H Sept.5,1972

51 int. Cl. ..l105b 11/00 53 riela 61 Search ..315 l06, 107, 305, 347; 219/121 EB [56] References flted UNITED STATES PATENTS 2,953,701 9/1960 Gale ..313/305 x 3,072,822 l/1963 Holmes ..315/107 3,158,733 11/1964 Sibley .250/495 0 3,250,893 5/1966 Nestor ..313/305 x Primary Examiner-Roy Lake Assistant Examiner-Darwin R. Hostetter Attorney-Holman & Stern [5 7] ABSTRACT A device for automatically controlling electrical conditions ofean electron bearnunit having an electron gun wherein a main cathode is heated by a current of electrons emitted by an auxiliary cathode, the main cathode of. the electron gun is supplied from a main 1969. cathode heating unit, the auxiliary cathode is supplied from an auxiliary cathode heating unit and a heating Foreign Application Priority D t correction unit of said main cathode is connected to at l f (1 ts. July 17, 1968 ussa. ..l257961 east Sal 1 Claim, 2 Drawing Figures [1.8. Cl....L .315/1116, 219/121 EB, 315/107,

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DEVICE FOR AUTOMATICALLY CONTROLLING ELECTRICAL CONDITIONS OF AN ELECTRON BEAM UNIT This application is a continuation of Ser. No. 841,8l6filed July 15, 1969.

The present invention relates to electrothermics, more particularly, to devices for automatically controlling electrical conditions of electron beam units having electron guns.

There exist devices for automatically controlling electrical conditions of an electron beam unit having an electron gun wherein the main cathode is heated by a current of electrons emitted by an auxiliary cathode, the main cathode of the gun being supplied from a main cathode heating unit, and an auxiliary cathode, from an auxiliary cathode heating unit.

A disadvantage of these devices is that they do not provide the required stability of the electrical conditions of an electron beam unit having an electron gun when the vapors of the metal'being heated condense on the surface of the cathode or when the cathode temperature changes under the influence of positive ions which bombard the cathode surface or under the influence of a thermal flux resulting from radiation of heat from the surface of the body being heated.

An object of the present invention is to obviate the above disadvantages by providing a device for automatically controlling electrical conditions of an electron beam unit having an electron gun which would increase the stability of the electrical conditions when the cathode emission decreases due to condensation on its surface of the vapors of the material being heated or when the cathode temperature changes due to the bombardment of the cathode surface by a current of positive ions or due to the appearance of a thermal flux resulting from radiation of heat from the surface of the article being heated.

With this object in view a device for automatically controlling electrical conditions of an electron beam unit having an electron gun wherein the main cathode is heated by a current of electrons emitted by an auxiliary cathode and the main cathode of the gun is supplied from a main cathode heating unit while an auxiliary cathode is supplied from an auxiliary cathode heating unit comprises, according to the invention, a main cathode heating correction unit connected to at least one of said heating units.

The main cathode heating correction unit must be preferably connected both to the main cathode heating unit and to the auxiliary cathode heating unit which must be made adjustable.

The device described herein makes the electrical operating conditions of the electron beam unit more stable, increases the efficiency of the unit and improves the quality of the finished article.

The invention will be best understood from the following description when read in connection with the accompanying drawings, in which:

FIG. 1 is a block diagram of a device for automatically controlling electrical conditions of an electron beam unit;

FIG. 2 is a diagram of one specific embodiment of the invention.

It is well known that the temperature of the emitting cathode surface depends on both on the power which is consumed from the cathode power source for heating the cathode and on the radiation flux from the surface of the article being heated.

Sometimes the emitting surface of the main cathode of an electron gun and the surface of the article being heated are located with in the zone of mutual irradiation.

Changes in the temperature of the surface of the article being heated or in the coefficient of mutual irradiation between the surfaces of the cathode and of the article (which occur, for example, in melting furnaces when the material being melted is fed to the zone of the electron beam) vary the resultant thermal flux from the surface of the article to the cathode. As a result, the temperature of the emitting surface of the cathode changes whereby affecting the power of the unit.

Another factor which affects the temperature of the emitting surface of the cathode and, consequently, the power of the unit is the varying intensity of the ion current to the cathode caused by fluctuation of the pressure and composition of the gases in the working chamber. I

It must be noted that as long as the power of the source supplying the main cathode remains unchanged, the power of the electron beam unit may deviate from a stable value only when the electron gun operates without space-charge limiting of the current. However, such operating conditions are typical for most industrial units in view of the fact that their power has to be adjustable and also because a number of technical difficulties are involved in heating purely metallic cathodes to temperatures at which the gun can operate with space-charge limiting of the current.

Power fluctuation caused by changes in the temperature of the emitting cathode surface which results from radiation of heat from the surface of the article and from the influence of the ion current affects the efficiency of the electron beam unit and the quality of finished articles.

In such cases an operator must interfere to restore the rated operating conditions of the unit.

Referring to the accompanying drawing (FIG. 1), an electron gun I is supplied from an electron gun source 2. A main cathode of the electron gun I is'supplied from a main cathode heating unit 3 which comprises a means 4' (FIG. 2) controlling the operating conditions of the heating unit. An auxiliary cathode of the electron gun I is supplied from an auxiliary cathode heating unit 5 which comprises a means 6 controlling its operating conditions. A main cathode heating correction unit 7 is connected to the output of the source 2 supplying the electron gun 1.

In the embodiment shown in FIG. 2 the supply source 2 of the electron gun 1 comprising a rectifier 8 and a transformer 9 connected through terminals 10, 11 and 12 to a supply line, is connected to the electrodes of the electron gun I.

The main cathode heating unit 3 comprising a rectifier 13, a transformer 14 connected through terminal 15 and 16 to the supply line of series-parallel thyristors 17 and 18, and a means 4 controlling the operating conditions is connected to the main and auxiliary cathode of the electron gun 1.

The auxiliary cathode heating unit 5 comprising a transformer 19, a series-parallel thyristors 20 and 21 and a system 6 controlling the operating conditions is connected to the supply line through terminals 22 and 23.

The device operates as follows. When the supply current or voltage of the electron gun 1 changes, a signal is applied from the output of the source 2 supplying the electron gun I to the main cathode heating correction unit 7 from which a correction signal is furnished to the main cathode heating unit 3 and the auxiliary cathode heating unit 5. The means 4 and 6 controlling the operating conditions operate the final control elements of the main cathode heating unit 3 and the auxiliary cathode heating unit in such a way that the power of the main cathode supply source and, consequently, the cathode temperature will keep changing until the current or voltage of the electron gun settles at the preassigned level.

Whenever one of the units, say, the main cathode heating unit 3, operates with regulation of the main cathode voltage or current, the signal from the main cathode heating correction unit 7 may be applied only to the auxiliary cathode heating unit 5 which remainsadjustable.

From the above description and the accompanying drawings it is clear that the use of the main cathode heating correction unit 7 in the device described herein makes it possible automatically to vary the power of the main cathode supply source and, consequently, the temperature of the emitting surface of the main cathode depending on the signal applied from the output of the power supply source 2.

We claim:

1. In a device for automatically controlling electrical conditions of an electron beam unit heating an element, the electron beam unit having an electron gun supply having an electron gun wherein a main cathode is heated by a current of electrons emitted by an auxiliary cathode, the improvement comprising a main cathode heating unit supplying said main cathode, an auxiliary cathode heating unit supplying said auxiliary cathode, and a main cathode heating correction means coupled between the electron gun supply and at least one of said heating units, said heating correction means detecting deviations of the current flowing between the main cathode and the element to be heated, said correction means varying the heating conditions of the main cathode in response to said deviations to stabilize the current by varying the power output of said at least one heating unit. 

1. In a device for automatically controlling electrical conditions of an electron beam unit heating an element, the electron beam unit having an electron gun supply having an electron gun wherein a main cathode is heated by a current of electrons emitted by an auxiliary cathode, the improvement comprising a main cathode heating unit supplying said main cathode, an auxiliary cathode heating unit supplying said auxiliary cathode, and a main cathode heating correction means coupled between the electron gun supply and at least one of said heating units, said heating correction means detecting deviations of the current flowing between the main cathode and the element to be heated, said correction means varying the heating conditions of the main cathode in response to said deviations to stabilize the current by varying the power output of said at least one heating unit. 